In a semiconductor device mounted on a circuit board for electronic equipment, its manufacturing method conventionally followed through the procedures:                i) circuit pattern forming on a semiconductor wafer and dividing it into each element,        ii) connecting lead frame pins or metallic bumps to electrodes for external connection of a element and,        iii) packaging the entire element including the connected parts with molding resin.        
In recent years, however, the method, in which packaging with the molding resin is performed before cutting the wafer, has been popular. According to the method, a resin layer is formed on a surface of a wafer to make a two-layer structure of the wafer and the resin layer. After that, electrodes for external connection including metallic bumps are formed on the structure. For forming metallic bumps, the method in which a conductive ball is mounted on the resin layer is generally employed.
In the two-layer structure having the resin layer over the wafer, there is a big difference in thermal expansion between silicon, which is the main material of the wafer, and the resin material. The structure often causes distortion due to thermal deformation through the addition of heat to the structure. Because of the distortion, a clearance appears partially between the surface of the resin layer and the bottom of a conductive ball held by a carrying head in the step of mounting the conductive ball onto the resin layer. It has therefore been difficult to appropriately mount conductive balls onto the clearance-developed area. That is, the clearance causes conductive balls to slip or fallout from the right proper position to be mounted, when conductive balls are set onto the surface of the resin layer and released from the carrying head sucking them by vacuum.
The object of the present invention is to provide a manufacturing method of a semiconductor device by protecting a semiconductor wafer from deformation, whereby conductive balls are properly mounted on the wafer.